Seeking experienced professional advice! Having a possible transmission issue. I have a 96' Chevy Tahoe (4x4, 2 door, 1500 series, V8, 190,000 miles) thats making a "shoosh" kinda noise only in first gear....
The pump in the front of the transmission can make this kind of noise, and one of the possible causes can be oil (fluid) starvation. Read this all the way through before you begin: Check the following: with engine hot and idling, transmission in park, and vehicle on level ground, check the transmission fluid level. Sometimes, with a very low level, like, off the stick low, you can hear a noise like this (but it is usually accompanied by sluggish or no transmission engagement, and sluggish or no shifting). Since you obviously don't have the shifting problems, it probably is not this low. Next, with your hands just-washed clean, rub some of the fluid from a wiped and re-inserted and withdrawn dipstick between your thumb and forefinger. Transmission fluid does not feel like soap-oily, it is more like hydraulic fluid, so it should feel wet and grippy, but not gritty. If it feels gritty, next examine some of the fluid, again from a fresh dip, under a strong light. It should be reddish-brown, clear and shiny, but should not sparkle like glitter. Finally, smell the fluid, again from a fresh sample. It should smell like hot hydraulic fluid, but should not smell burnt. If it is, you will know it when you smell it. Nothing else smells like burned transmission oil.
If you have clear, reddish-brown, grit-free transmission fluid, the only step left for you to try is to change the transmission fluid and filter. This will cost you about 20 bucks, and will take you about an hour. There are 13 bolts that hold the transmission pan onto the transmission case, usually 10mm size. Place a large catch-pan of about 3 gallon capacity directly under the transmission pan. Some models have a drain plug in the transmission pan, and some don't, and it varies with Chevrolet even in the same model-year. If it has a drain plug, great, remove it and drain the oil from the transmission pan, then remove the bolts, the pan, the gasket, and then the filter. The filter just snaps into the valve body by interference fit with an o-ring on the filter orifice. (Examine your new one before you begin to familiarize yourself with the filter.) Be sure you get the right filter; there are two, a shallow pan and a deep pan version. Measure the depth of the pan from the bolt flange to the bottom of the pan and tell the parts guy how many inches deep it is. He'll know. Buy only the AC/Delco brand. It comes with the new pan gasket, and is the factory-correct filter for you truck.
If you don't have a drain plug, loosen all the bolts about a quarter-inch along the front edge, and left and right sides, but NOT the rear edge. With a thin putty knife, gently pry the front of the pan until the gasket breaks loose. You will have a wave of fluid exit the pan quite forcefully, so be sure your catch-pan is both big enough and far forward enough to capture the fluid as it drains from the pan. After it has drained down to drips, remove the bolts from the front edge, and about half of them from the left and right sides, and loosen the bolts at the back edge; let more fluid out. Finally remove the rest of the bolts and remove the pan from the transmission case. Invert the pan, and drain the rest of the fluid from it. With the thin putty knife, gently remove all the old gasket material from the bottom of the transmission case. Next, take the pan out from under the vehicle, turn it back right-side-up, and look at the inside floor of the pan. There is a magnet inside the pan. It is customary for there to be a thick beard of metallic filings on this magnet. This is not a problem as long as the filings feel very fine. It should almost feel like you are rubbing your fingers in smooth peanut butter. If this is what you find, carefully remove all the old gasket material from the transmission pan, remove the old fluid filter from the valve body (it will be much heavier than the new one because it is full of filings and oil), and replace the new filter exactly like the old one was. Install the new gasket on the pan, replace the pan, torqueing the pan bolts to 13 inch pounds each, working in a criss-cross pattern until all bolts are torqued equally. Add 3 quarts of new Dexron III transmission fluid through the transmission dipstick tube using a paper transmission fluid funnel with the built-in stariner on the narrow end, then check the fluid leve. Start the engine for thirty seconds, then shut off. Check the fluid level again. If it is still low, re-start the engine, and begin adding a small amount at a time, leaving the engine running and checking the level after each addition until the proper level is read from the dipstick. If you overfill it, don't worry---the transmission has vents which will puke out the excess.
If, however, the beard on the pan magnet feels like chunky peanut butter, or if you see slivers or chunks of metal in the pan or on the magnet, don't bother with the filter change: put the pan back on without the gasket, and call a tow truck to carry it to a transmission repair facility. Hard parts in the pan mean "Rebuild me today!" Tell the builder you want The Beast sun shell, Alto Red Eagle frictions and Kolene steels throughout, a new reverse drum and Carbon Fiber power band, and Sonnax "Super Hold" 1-2 & 3-4 servos as a minmum above a stock rebuild, and you yourself add a 15,000lb capacity auxilliary transmission fluid cooler in addition to the cooler built into the radiator, and your new transmission will be bullet-proof. It will also feel like the truck has just gotten about a hundred extra horsepower added to it, even though you haven't touched the engine. None of these extras require any machining to install, so don't let anyone work on it who claims it does.
I have built many of these 4L60E transmissions, and the key to long life is to change the fluid and filter every 50,000 miles, and when they die, build them back stronger than stock.
And never put any additive of any kind in one--it's just snake oil and won't fix a thing.
Feb 16, 2010 |
Chevrolet Tahoe Cars & Trucks